<template>
<scroll @scroll="scroll" :listen-scroll="listenScroll" :probe-type="probeType" :data="data" class="listview" ref="listview">
  <ul>
    <li v-for="group in data" class="list-group" ref="listGroup">
      <h2 class="list-group-title">{{group.title}}</h2>
      <uL>
        <li @click="selectItem(item)" v-for="item in group.items" class="list-group-item">
          <img class="avatar" src="../assets/img/person.png">
          </img>
          <span class="name">{{item.name}}</span>
        </li>
      </uL>
    </li>
  </ul>
  <div class="list-shortcut" @touchstart.stop.prevent="onShortcutTouchStart" @touchmove.stop.prevent="onShortcutTouchMove" @touchend.stop>
    <ul>
      <li v-for="(item, index) in shortcutList" :data-index="index" class="item" :class="{'current':currentIndex===index}">{{item}}
      </li>
    </ul>
  </div>
  <div class="list-fixed" ref="fixed" v-show="fixedTitle">
    <div class="fixed-title">{{fixedTitle}} </div>
  </div>
  <div v-show="!data.length" class="loading-container">
    <!-- <loading></loading> -->
  </div>
</scroll>
</template>

<script>
import Scroll from './Scroll'
// import Loading from 'base/loading/loading'
import {
  getData
} from '@/utils/dom'

const TITLE_HEIGHT = 30
const ANCHOR_HEIGHT = 18

export default {
  props: {
    data: {
      type: Array,
      default: []
    }
  },
  computed: {
    shortcutList() {
      return this.data.map((group) => {
        return group.title.substr(0, 1)
      })
    },
    fixedTitle() {
      if (this.scrollY > 0) {
        return ''
      }
      return this.data[this.currentIndex] ? this.data[this.currentIndex].title : ''
    }
  },
  data() {
    return {
      scrollY: -1,
      currentIndex: 0,
      diff: -1,
      listenScroll: true,
      probeType: 3,
      touch: {}
    }
  },
  created() {
    this.probeType = 3
    this.listenScroll = true
    this.touch = {}
    this.listHeight = []
  },
  methods: {
    selectItem(item) {
      this.$emit('select', item)
    },
    onShortcutTouchStart(e) {
      let anchorIndex = getData(e.target, 'index')
      let firstTouch = e.touches[0]
      this.touch.y1 = firstTouch.pageY
      this.touch.anchorIndex = anchorIndex
      this._scrollTo(anchorIndex)
    },
    onShortcutTouchMove(e) {
      let firstTouch = e.touches[0]
      this.touch.y2 = firstTouch.pageY
      let delta = (this.touch.y2 - this.touch.y1) / ANCHOR_HEIGHT | 0
      let anchorIndex = parseInt(this.touch.anchorIndex) + delta

      this._scrollTo(anchorIndex)
    },
    refresh() {
      this.$refs.listview.refresh()
    },
    scroll(pos) {
      this.scrollY = pos.y
    },
    _calculateHeight() {
      this.listHeight = []
      const list = this.$refs.listGroup
      let height = 0
      this.listHeight.push(height)
      for (let i = 0; i < list.length; i++) {
        let item = list[i]
        height += item.clientHeight
        this.listHeight.push(height)
      }
    },
    _scrollTo(index) {
      if (!index && index !== 0) {
        return
      }
      if (index < 0) {
        index = 0
      } else if (index > this.listHeight.length - 2) {
        index = this.listHeight.length - 2
      }
      this.scrollY = -this.listHeight[index]
      this.$refs.listview.scrollToElement(this.$refs.listGroup[index], 0)
    }
  },
  watch: {
    data() {
      setTimeout(() => {
        this._calculateHeight()
      }, 20)
    },
    scrollY(newY) {
      const listHeight = this.listHeight
      // 当滚动到顶部，newY>0
      if (newY > 0) {
        this.currentIndex = 0
        return
      }
      // 在中间部分滚动
      for (let i = 0; i < listHeight.length - 1; i++) {
        let height1 = listHeight[i]
        let height2 = listHeight[i + 1]
        if (-newY >= height1 && -newY < height2) {
          this.currentIndex = i
          this.diff = height2 + newY
          return
        }
      }
      // 当滚动到底部，且-newY大于最后一个元素的上限
      this.currentIndex = listHeight.length - 2
    },
    diff(newVal) {
      let fixedTop = (newVal > 0 && newVal < TITLE_HEIGHT) ? newVal - TITLE_HEIGHT : 0
      if (this.fixedTop === fixedTop) {
        return
      }
      this.fixedTop = fixedTop
      this.$refs.fixed.style.transform = `translate3d(0,${fixedTop}px,0)`
    },
  },
  components: {
    Scroll,
    // Loading
  },
  created(){
    this.$nextTick(()=>{
      this._calculateHeight()
    })
  }
}
</script>

<style scoped lang="less">
@import '../styles/variables.less';

.listview {
    position: relative;
    width: 100%;
    height: 100%;
    overflow: hidden;
    // background: @color-background;
    .list-group {
        .list-group-title {
            height: 0.36rem;
            line-height: 0.36rem;
            padding-left: 0.3rem;
            // font-size: @font-size-small;
            // color: @color-text-l;
            // background: @color-highlight-background;
            font-size: 0.24rem;
            color: #999999;
            background: #f2f2f2;
        }
        .list-group-item {
              height: 1rem;
              line-height: 1rem;
              display: flex;
              align-items: center;
              background-color: #fff;
              border-bottom: 0.01rem solid #a6a6a6;
            .avatar {
                width: 0.38rem;
                height: 0.38rem;
                margin: 0.11rem 0.26rem 0.11rem 0.3rem;
                /* padding: 0.11rem 0.26rem 0.11rem 0.3rem; */
                border-radius: 2%;
            }
            .name {
                // color: @color-text-l;
                // font-size: @font-size-medium;
                color: #333333;
                font-size: 0.32rem;
            }
        }
    }
    .list-shortcut {
        position: absolute;
        z-index: 30;
        right: 0;
        top: 50%;
        transform: translateY(-50%);
        width: 0.4rem;
        padding: 0.4rem 0;
        border-radius: 0.2rem;
        text-align: center;
        // background: @color-background-d;
        background-color: transparent;
        font-family: Helvetica;
        .item {
            padding: 0.06rem;
            line-height: 1;
            // color: @color-text-l;
            // font-size: @font-size-small;
            color: #808080;
            font-size: 0.28rem;
        }
        .item.current {
            // color: @color-theme;
            color: #fa8e00;
        }
    }
    .list-fixed {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        .fixed-title {
            height: 0.4rem;
            line-height: 0.4rem;
            padding-left: 0.4rem;
            // font-size: @font-size-small;
            // color: @color-text-l;
            // background: @color-highlight-background;
            font-size: 0.28rem;
            color: #999999;
            background: #f2f2f2;
        }
    }
    .loading-container {
        position: absolute;
        width: 100%;
        top: 50%;
        transform: translateY(-50%);
    }
}
</style>
